1. Field of the Invention
Aspects of the present invention relate to a multiple input multiple output (MIMO) communication system, and more particularly, to a closed-loop communication control scheme that can feed back channel information from a user equipment to a base station.
2. Description of the Related Art
A multiple input multiple output (MIMO) communication system is a system that can transmit and receive data between at least one base station and at least one user equipment. In the MIMO communication scheme, since each base station and user equipment includes a plurality of antennas, it is possible to improve the efficiency of transmitting and receiving data.
The MIMO communication system can simultaneously transmit data from the base station to the user equipment using a plurality of antennas and also may improve a transmission rate of information by a spatial division multiple access (SDMA) scheme. The SDMA scheme allocates a plurality of spatial beams to the user equipment and transmits data to the user equipment using each of the spatial beams. A process of allocating the spatial beams is referred to as “precoding” or “beamforming.” A precoding process or a beamforming process may be performed through the computation with respect to a matrix or a vector.
The precoding process or the beamforming process can adopt a scheme in which a base station is aware of information about a communication channel that reaches a user equipment, or a scheme in which a user equipment can feed back channel information to a base station. A channel information feedback scheme is a closed-loop communication control scheme.
The closed-loop communication control scheme is advantageous in that it is possible to accurately reflect a channel state changing over time. However, a user equipment included in a communication system should compute a channel feature according to the change of the channel state. Therefore, hardware of the user equipment becomes complex.
Accordingly, there is a need for an apparatus and method of generating a codebook that can maintain advantages of a closed-loop communication control scheme applied in a MIMO communication system and also can be easily realized in hardware of a user equipment.